1. Field of the Invention
The present invention relates to a library apparatus for accommodating a plurality of types of recording medium. More specifically, the present invention relates to a library apparatus having a construction for reading markers on recording media at high speed and a method for reading the markers.
2. Description of Related Art
A library apparatus is essential for various information processing systems which are capable of storing and processing vast quantities of data. The vast quantities of data are stored in many recording media such as magnetic tapes, which are accommodated in a library apparatus.
Each of the magnetic tapes is used by accommodating it in a cartridge: hereinafter, the cartridge accommodating a magnetic tape will be just referred to as a cartridge. The cartridges are individually accommodated in a cell of a cabinet in the library apparatus. Writing/reading of data is performed for a corresponding magnetic tape cartridge among many magnetic tape cartridges, on the basis of read/write commands from a host device.
More specifically, a cell which accommodates the corresponding cartridge is specified in the library apparatus based on the command from the host device. Then, the cartridge accommodated in this cell is conveyed to a recording/reproducing device in the library apparatus by a conveyor known as an accessor having a holding function for grabbing and holding a cartridge and a conveying function, the cartridge is loaded therein, and then reading/writing of data is performed from/to the magnetic tape.
Herein, each cartridge accommodated in the library apparatus corresponds to the position of each cell for accommodating the cartridge, and thus there is no need to search for a corresponding cartridge every read/write processing.
The correspondence between the cartridge and the cell is performed in the following way. A barcode label, on which volume label information such as a serial number is recorded, is attached to each cartridge. This barcode label is read by a reader mounted in the accessor when each cartridge is accommodated in the library apparatus. The reading is performed in the following way: the reader radiates reading light onto the label so as to scan it, receives reflection light generated by modulation by the barcode, and the reflection light is transformed to an electrical signal for signal processing.
The reading is performed when the movement of the reader is stopped. When the reader fails to read the barcode, it moves again to change the scanning position of the reading light so as to read the barcode. In this way, the reader repeatedly reads the barcode, the cartridge is accommodated in an empty cell after the reader obtains correct barcode data, the cell is associated with a volume label, and the correspondence relationship is transmitted to the host device. After that, the host device transmits a command including information of a cell to be accessed to the library apparatus, and then the accessor accesses the cartridge in the cell.
In this way, the volume label of the cartridge is read when the cartridge is accommodated in the library apparatus (hereinafter, xe2x80x9ca cartridge is insertedxe2x80x9d means a cartridge is accommodated in the library apparatus and xe2x80x9ca cartridge is ejectedxe2x80x9d means a cartridge is taken out from the library). Even when a large number of cartridges are inserted at one time, the volume label of each cartridge preferably should be read quickly and accurately.
On the other hand, the quantity of data processed in information processing devices has become larger and larger and the storage capacity of various recording media has become larger. In magnetic tapes, 128-track magnetic tapes are becoming more common than conventional 36-track magnetic tapes in order to increase the storage capacity. A 128-track magnetic tape can be accommodated in a cartridge whose shape is substantially the same as that for a 36-track magnetic tape.
The storage capacity of the library apparatus increases by using 128-track magnetic tapes. However, cost and time are required to transfer the data stored in conventional 36-track magnetic tapes to 128-track magnetic tapes.
Accordingly, a library apparatus in which 36-track magnetic tapes can continue to be used and 128-track magnetic tapes can be used in combination with the 36-track magnetic tapes has been desired.
On the other hand, as the types of magnetic tape increase, information for distinguishing the types is required as well as the volume label. Accordingly, the amount of identification information recorded on a cartridge label increases. Read errors will be more likely to occur as the identification information increases. Therefore, a method for enabling higher-speed reading is desired so as to shorten the time for read processing even when a read error occurs.
It is an object of the present invention to provide a library apparatus in which the above-described different types of magnetic tape can be used in combination. Further, it is an object of the present invention to provide a method for reading markers on the different types of magnetic tape, that is, a method for reading the type of the magnetic tape and its volume label.
Reading processing takes time because rereading is performed when a read error occurs and because a reader is started from a stop mode for reading the barcode label of the next cartridge. Accordingly, in the present invention, markers such as various labels attached on a recording medium such as a magnetic tape are read by a moving reader. When the read data includes the data of all types of marker, it is determined that the markers are accurately read. When the data does not include the data of all types of markers, reading is continued. With this arrangement, retry processing can be performed by moving the reader without restarting it from the stop mode.
Also, in the present invention, the above-described reading is performed when the recording medium is accommodated in the library apparatus. With this arrangement, reading of the markers can be performed in a short time even when a large number of recording media are accommodated.
Further, in the present invention, means for setting the type of the recording medium is provided in an accommodation unit for accommodating the recording medium in the library apparatus. With this arrangement, the type of the recording medium is clear when reading of the markers on the recording medium is performed in advance, and thus preferable retry processing for each recording medium can be performed and reading of the markers can be performed in a short time.